1. Field of the invention
The invention relates to a torsional damper device for torque transmission systems such as clutches; it is more particularly concerned with improvements to certain elements of two coaxial parts able to rotate relative to each other to a limited degree.
2. Description of the prior art
A torque transmission system such as a friction clutch designed to be inserted between the crankshaft of the motor and the input shaft of the gearbox in an automobile vehicle usually comprises a torsional damper device adapted to absorb variations in this torque to avoid vibration and in particular audible vibration arising at any point along the kinematic system in which said torsional damper device is inserted. A damper device of this kind is often combined with the friction disk of the clutch or with the inertia flywheel driven by the crankshaft of the motor and also serving as a reaction plate for the clutch.
French Pat. No. 2 571 461 describes a torsional damper device of this kind combined with an inertia flywheel. The flywheel comprises two coaxial parts between which are circumferentially disposed helical coil springs. To be more precise, each spring is held between base members pivotally mounted between two flanges (also called guide rings) of a first part, in this instance the driving part, while the same base members are adapted to be loaded circumferentially with the possibility of articulation by annular metal plates fastened to the driven part, variation in the compression of the springs absorbing variations in torque and procuring some degree of filtering of vibrations of all kinds.
This system gives good results, principally because of the pivoted base members which enable the springs to function under optimum conditions by preventing them being subjected to excessive radial deformation inwards or outwards. However, impacts between the base members on the one hand and the flanges and plates on the other hand are somewhat audible. Also, said base members being molded from a plastics material, the parts of the flanges and plates which cooperate with said base members have to be cut out accurately, free of any burrs, to avoid deterioration of the areas of the base member with which they interact. The flanges and plates are therefore relatively costly to manufacture, since they cannot be made simply by cutting out with a hollow punch.
An object of the invention is to reduce operating noise in a torsional damper device of this kind.
Another object of the invention is to make it possible to manufacture the flanges and plates of this torsional damper device at reduced cost.